The present invention relates to a system switching control method, and, more particularly, to a switching control method of a database server when a fault occurred in a database management system, and, furthermore, to database recovery processing.
A system switching technique is adopted as a means of improving the availability of a database management system. The system switching technique recovers system processing by switching processing of a machine (otherwise, a computer or an information processing unit, or a server) in which a fault occurred to another machine, and reduces a service stop time caused by the fault.
In a database management system to which system switching control is applied, a machine that functions as a switching target for a fault for every machine that executes a service is defined. When the database management system detects the fault of an executive system (application system) machine, the system is switched to a standby system machine. As this type of technique, for example, such a technique disclosed in Japanese Published Unexamined Patent Application No. 2001-282763 is available.
The system switching first allows an executive system resource, for example, a disk that stores a database or a network address to be switched to a standby system machine. When the resource switching is completed, the standby system executes database recovery processing with reference to a log of the database which a database server inherited from an executive system. When the database recovery processing is completed, the standby system starts service acceptance and functions as the executive system, then completes the system switching. A technique like this is described in “TRANSACTION PROCESSING: CONCEPTS AND TECHNIQUES” by Jim Gray and Andreas Reuter, Morgan Kaufmann Publishers, 1993.
When multiple database servers apply system switching to a database management system that operates on the same machine, the multiple database servers on the machine in which a fault occurred are mostly switched to separate machines. When multiple machines share and inherit the processing of the machine in which a fault occurred, a load that appears during the fault is dispersed, a load increase in a switching target machine is suppressed. A technique like this is described in “Implementing IBM DB2 Universal Database V8.1 Enterprise Server Edition with Microsoft Cluster Server” by Aslam Nomani, International Business Machines Corporation, 2003, FIG. 16 (Pages 40 and 41) [online], [Retrieved on Dec. 19, 2003], <http://www-306.ibm.com/software/data/pubs/papers/esemcs/e semcs.pdf>.